Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$40.64	3.606%	$42.1055	$42.11	$42.10	$42.10
Purchase #2	$76.71	8.367%	$83.1283	$83.13	$83.15	$83.10
Purchase #3	$216.65	3.532%	$224.3021	$224.30	$224.30	$224.30
Purchase #4	$47.39	9.862%	$52.0636	$52.06	$52.05	$52.10
Purchase #5	$95.46	10.782%	$105.7525	$105.75	$105.75	$105.80
Purchase #6	$221.42	5.405%	$233.3878	$233.39	$233.40	$233.40
Purchase #7	$11.34	7.306%	$12.1685	$12.17	$12.15	$12.20
7 purchase totals =	$709.61		$752.9083	$752.91	$752.90	$753.00